Add problem 875: Koko Eating Bananas

Author: EFanZh

src/lib.rs

@@ -717,6 +717,7 @@ pub mod problem_0869_reordered_power_of_2;
 pub mod problem_0870_advantage_shuffle;
 pub mod problem_0872_leaf_similar_trees;
 pub mod problem_0874_walking_robot_simulation;
+pub mod problem_0875_koko_eating_bananas;
 pub mod problem_1143_longest_common_subsequence;
 pub mod problem_1192_critical_connections_in_a_network;
 pub mod problem_1342_number_of_steps_to_reduce_a_number_to_zero;

src/problem_0875_koko_eating_bananas/binary_search.rs

@@ -0,0 +1,63 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    fn div_ceil(lhs: u32, rhs: u32) -> u32 {
+        let result = lhs / rhs;
+
+        if lhs % rhs == 0 {
+            result
+        } else {
+            result + 1
+        }
+    }
+
+    fn check(piles: &[i32], h: u32, speed: u32) -> bool {
+        piles.iter().map(|&pile| Self::div_ceil(pile as _, speed)).sum::<u32>() > h
+    }
+
+    pub fn min_eating_speed(piles: Vec<i32>, h: i32) -> i32 {
+        let h = h as u32;
+        let mut total = 0;
+        let mut max = 0;
+
+        for &pile in &piles {
+            let pile = pile as u32;
+
+            total += pile;
+            max = max.max(pile);
+        }
+
+        let mut low = Self::div_ceil(total, h);
+        let mut high = max;
+
+        while low < high {
+            let middle = (low + high) / 2;
+
+            if Self::check(&piles, h, middle) {
+                low = middle + 1;
+            } else {
+                high = middle;
+            }
+        }
+
+        low as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn min_eating_speed(piles: Vec<i32>, h: i32) -> i32 {
+        Self::min_eating_speed(piles, h)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_0875_koko_eating_bananas/mod.rs

@@ -0,0 +1,22 @@
+pub mod binary_search;
+
+pub trait Solution {
+    fn min_eating_speed(piles: Vec<i32>, h: i32) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [
+            ((&[3, 6, 7, 11] as &[_], 8), 4),
+            ((&[30, 11, 23, 4, 20], 5), 30),
+            ((&[30, 11, 23, 4, 20], 6), 23),
+        ];
+
+        for ((piles, h), expected) in test_cases {
+            assert_eq!(S::min_eating_speed(piles.to_vec(), h), expected);
+        }
+    }
+}